1. Field of the Invention
The Invention concerns a measuring device for carrying out luminescence measurements, in particular chemiluminescence and/or fluorescence measurements of fluid samples, with a light detector, in particular a photo-multiplier for receiving light emitted from an upwardly directed measurement opening of a sample container on an entry surface.
2. Description of the Related Art
Measurement devices of this type are employed above all in chemical, clinical and environmental analysis for research, in which high sensitivity and selectivity for the substances to be detected are necessary. The detection principal is based upon the detection of the light signal, which is emitted from an analyte which has been stimulated by a chemical reaction or by a irradiation with excitation or activation light to chemiluminescence or as the case may be fluorescence emissions. Thereby it is known to measure measurement light emitted from a sample container via a diaphragm with a photo-multiplier, of which the face side entry window is concentric with the sample container opening in the vertical separation to this is provided. As a disadvantage it can be seen that by the vertical upwardly directed longitudinally extending photo-multiplier the construction height of the measurement device is substantially increased. In addition the supporting or mounting of the detector in a vertical position is more difficult.
In order to avoid these problems, it is known with a similar measurement device, that the measurement light is coupled to the measurement opening of an optical fiber, of which the emissions side is coupled to a photo-multiplier. In this manner it is on the one hand possible to avoid limitations in the design of the photo-multiplier, however they occur in the use of a fiber optic besides the worsening of the projection quality, substantial losses in the light yield. Besides this the optical fiber impedes the in certain cases necessary access of additional construction elements in the area of the measurement opening.